The present invention relates to pipe insulation, and more particularly to a method and apparatus for applying adhesive to the edges of a slit extending along a tubular body of pipe insulation.
Flexible foam pipe insulation is well known in the art. The insulation is usually formed into a tube by extruding a foamed polymeric material, such as polyethylene, polypropylene, vinyl resin, polyurethane, polystyrene, or other related plastic materials. The extruded tube typically has a microcellular composition created by adding a blowing or foaming agent to the polymeric material. The blowing or foaming agent is incorporated into the polymeric material at a higher pressure and foams as the pressure is reduced, such as when the polymeric material passes through a die head during the extrusion process.
Typically, the tube is then cut into sections and allowed to cure to solidify the microcellular structure of the foamed polymeric material. After the tube has cured, further processing is performed. Conventionally, the tube is slit longitudinally by a slitter, such as a stationary or rotating blade. Glue or adhesive is also applied to the edges of the slit so that the edges can be secured together once the tube is placed around a pipe that is desired to be insulated.
One problem suffered by conventional systems is a poor approach to forming the longitudinal slit in the tube. The slit is typically formed by feeding the tube through the slitter such that the slitter penetrates into the hollow center portion of the tube. As the tube is slit, the edges rub against the slitter, thus generating a high amount of friction and heat. This is especially true when the slitter is a rotating cutting blade. Rotating cutting blades have certain advantages, such as an ability to stay sharper longer than stationary blades. However, the frictional forces generated between the slitter and the edges of the slit can be severe. As a result, the tube tends to deform into a curved shape because the heat generated by the friction causes the polymeric material to constrict along the slit. Some systems attempt to compensate for the deformation problem by providing complex supporting devices. In particular, mandrels having passages with cooling air and/or cooling water often are used to cool the tube while forcing the tube to remain in a tubular form during processing. However, these systems involve high complexity and cost.
Another problem found in conventional systems is in applying the adhesive to the edges of the slit. In particular, puller or conveyor belts used to feed the tube through the slitter are also often used to advance the tube to a plow or roller for deforming the edges of the slit into a flat plane so that the adhesive can be sprayed or coated onto the edges. For example, U.S. Pat. No. 3,821,939 discloses an apparatus for flattening the tube so that the edges are in the same plane and a coating roll for applying adhesive to the two edges. A release liner, such as a silicone coated tape, is then applied to the slit edges to prevent the edges from adhering to each other before the tube is installed around a pipe. The tube is then allowed to return to the original tubular form so that the release liner is folded on itself between the edges of the slit. This method, however, results in extreme deformation of the tube and can result in damage to the tube caused by the collapsing or rupturing of the foamed polymeric material.
Another method for applying adhesive to the edges of the slit provides a wedging member in conjunction with a mandrel, which supports and cools the tube during processing. Such a method is disclosed in U.S. Pat. No. 5,558,739. The mandrel is sized slightly larger than the inner diameter of the tube, thus causing the edges of the slit to separate and define an acute angle therebetween. The wedging member is comprised of a pair of plates which converge at an angle matching that of the acute angle defined by the edges of the slit so that a pair of adhesive-coated tapes can be applied to the edges of the slit. This method, however, also includes the complexity and cost of a mandrel to support and cool the tube during processing. Moreover, the mandrel and wedging member must be sized to fit each tube being processed at a particular time. Accordingly, processing different sized tubes requires changing the mandrel and wedging member according to the inner diameter of each tube so that the mandrel spreads apart the edges of the slit at an appropriate acute angle and the wedging member converges at the same angle defined by the edges of the slit.
Thus, there is a need for providing a method and apparatus which avoids the problems in the prior art. More specifically, there is a need for providing a method and apparatus for slitting a tube of pipe insulation that results in frictional forces between the slitter and edges of the tube that are sufficiently low such that the tube does not substantially deform. There is also a need for providing a method and apparatus for applying an adhesive to the slit edges of a tube of pipe insulation without crushing or seriously deforming the tube to a significant degree. Such a method and apparatus would also advantageously be capable of forming a slit in a tube of pipe insulation and applying an adhesive to the slit edges thereof without internal support structures, such as mandrels and the like.
These and other needs are provided, according to the present invention, by a device having a housing member positioned such that the housing member covers at least a portion of the cutting blade and separates the edges of the slit from the cutting blade to reduce frictional engagement of the cutting blade with the edges of the slit. In addition, the housing member has exterior surfaces for receiving a pair of release tapes from tape feed paths and directing the release tapes along lines parallel to the path of travel of the tubular body so that the release tapes are adhered to the edges of the slit.
In particular, the apparatus of the present invention includes tape feeds for feeding the release tapes along tape feed paths toward the tubular body as the tubular body is advanced along a path of travel. The release tapes have an adhesive applied to at least one surface thereof. The apparatus also includes a cutting blade for cutting or slitting the tubular body as the tubular body is advanced past the cutting blade. More specifically, the housing member having the cutting blade mounted therein is positioned along the path of travel of the tubular body. As such, the slit is formed in the tubular body having a pair of opposed slit edges with the cutting blade interposed therebetween. The surfaces of the release tapes having the adhesive applied thereto are applied the edges of the slit as the release tapes are directed by the exterior surfaces of the housing member. In one embodiment, the cutting blade is a rotating cutting blade. In another embodiment, the cutting blade is stationary.
According to the present invention, the apparatus also includes an adhesive applicator for applying the adhesive to the release tapes. The apparatus may also include flared projections or thicker portions extending away from the housing member for providing urging forces against the release tapes and the corresponding edges of the slit.
Thus, the present invention provides a method and apparatus for applying adhesive to the edges of a slit tube wherein the tube is slit by a portion of the cutting blade exposed at the leading edges of the housing member such that very little frictional forces and heat are generated between the tube and the cutting blade during the slitting process. Furthermore, the present invention directs a pair of adhesive coated tapes around the leading edges of the housing member proximate the exposed portion of the cutting blade and along the parallel exterior surfaces thereof. As such, the present invention provides a novel approach for applying the adhesive to the edges of the tube having low complexity, low cost, and advantageous safety features.